The saddle-back tamarins are squirrel-sized New World monkeys from the family Callitrichidae in the genus or subgenus Leontocebus. They were split from the tamarin genus Saguinus based on genetic data and on the fact that saddle-back tamarins are sympatric with members of Saguinus to a greater extent than would be expected from two members of the same genus. Some authors still consider Leontocebus to be a subgenus of Saguinus.
In some locations saddle-back tamarins live sympatrically with tamarins of the genus Sanguinus, but the saddle-back tamarins typically occupy lower strata of the forest than do the Sanguinus species. Saddle-back tamarins have longer and narrower hands than Sanguinus species, possibly adaption to differing foraging behavior, as saddle-back tamarins are more likely to search for insects that are hidden in knotholes, crevices, bromeliad tanks and leaf litter, while Sanguinus species are more likely to forage for insects that are exposed on surfaces such as leaves or branches.